I. Field of the Invention
The present invention relates to medical implants. More particularly, this invention relates to suture anchors used to attach soft tissue to bone.
II. Related Art
Surgeons have employed various types of suture anchors for decades for a variety of surgical applications. Suture anchors provide a surgeon with a means for attaching two pieces of tissue together so that they may heal. The tissues typically are tendon, ligament, or bone.
Prior to the development of suture anchors, surgeons would typically pass the suture material directly through bone utilizing sharp, trocar-tipped needles. Clamps or other similar instruments were sometimes used instead of sutures. In either case, a rather large surgical exposure was required resulting in increased surgical morbidity to the patient and longer healing times. The advent of suture anchors allowed the refinement of a variety of surgical procedures. Rather than using a conventional, open approach requiring a large incision, the use of suture anchors permitted the surgeon to employ a minimally invasive arthroscopic approach leading to less surgical morbidity and potentially faster healing rates for patients.
Suture anchors typically comprise two components—the body of the anchor and a suture material to be anchored to the bone. The body of the anchor can be made of a variety of different materials that are biocompatible, easily sterilized and strong enough to withstand the forces that may be exerted on the anchor. Such materials include, without limitation, titanium, alloys of stainless steel, polyether-ether ketone (PEEK), poly-1-lactic acid, and other biocompatible materials. An example of a material used to form the sutures is a polyester braid. The suture material is used to join tissue to the anchor body and the anchor body couples the suture material to a bone, providing an “anchor point” to the bone.
Prior art suture anchors typically have one of several designs that permit the body of the suture anchor to be secured to the bone. Most of these designs incorporate a solid body with exterior threads or ridges. When the anchor is a solid body incorporating exterior threads, a pilot hole is typically drilled into the bone and then the anchor body is screwed into the pilot hole and the threads prevent the anchor body from pulling out of the bone. Similarly, when a solid anchor body having ridges is employed, a pilot hole is drilled and the anchor body is impacted into the bone such that the ridges prevent the anchor body from being pulled out. Some anchor bodies are designed to expand such that the entire body or an element of the body expands as the anchor body is driven into the bone to prevent the anchor body from being pulled out of the bone.
Commercial suture anchors may come preloaded with the suture material. Alternatively, loading the suture anchor with the suture material may be performed by the surgeon. When the suture anchor comes preloaded, the anchor body is typically placed into the bone at an anchor point and then the suture material is passed through or around a piece of tissue to be joined to the bone at the anchor point. The sutures are then tied, securing the piece of tissue to the anchor body which has already been placed in the bone at the anchor point. When the suture anchors are not preloaded with suture material, free sutures are typically passed by the surgeon through or around a piece of tissue that the surgeon wishes to anchor to the bone. The sutures are then fed through the anchor body and the anchor body is impacted into the bone pulling the tissue down to the anchor point.
The sutures are secured within the anchor body in various manners. In some situations, this fixation is made without tying knots and the anchor is referred to as a “knotless” anchor. When knotless anchors are used, an internal locking mechanism is provided such that the sutures are locked to the anchor body via the locking mechanism. The locking mechanism typically operates by pinching the sutures. In other cases, the sutures are extended between the bone and the external surfaces of the anchor body such that when the anchor body is inserted into the bone at the anchor point, the sutures are pinched between the bone and the anchor body.
While a number of surgical procedures have been successfully performed using prior art suture anchors, surgeons sometimes encounter difficulties implanting such suture anchors arthroscopically. Thus, to complete the surgical procedure, a large surgical exposure is created. This serves to increase trauma, pain, risk of nerve and tissue damage, and healing time. Further, during recovery and before healing is complete, excessive forces may be applied to the sutures and anchor body by the tendon, ligament or bone which can result in the suture anchor dislodging from the bone or the sutures dislodging from the anchor body. Additional surgical repair is required should such dislodging occur. Still further, upon removal or dislodging of currently existing suture anchors, a cylindrical defect is left in the host bone. Such a defect may serve as an impediment to placement of new anchors for revision surgery. Additionally, many “knotless” suture anchors have complex internal locking mechanisms that may present technical difficulties for the surgeon performing the procedure during actuation of the locking mechanism. As such, there is a real need for an improved suture anchor which can be readily and easily implanted arthroscopically, is simple to use, will be securely bound to the bone, and at the same time will securely couple the sutures to the anchor body and bone.